In the microelectronics industry, fabrication of electrical devices typically includes one or more steps that involve heating a substrate, circuit board, and/or lead frame. For example, a packaged integrated circuit may be fabricated by mounting a die carrying the integrated circuit on a package carrier that provides electrical connections from the die to the exterior of the package. The die includes an area array of electrically-conductive contacts, or bond pads, that are electrically connected to a corresponding area array of conductive contacts on the package carrier, known as solder balls or bumps. Typically, the solder bumps are registered with the bond pads and a reflow process is applied to create electrical connections in the form of solder joints between the die and the package carrier by heating the package. Similarly, electronic components may be electrically coupled to a circuit board by placing the components on the circuit board so that the components are positioned with electrical leads on contact pads that have been coated with a solder paste. The circuit board may then be heated so that the solder paste melts or reflows, thereby coupling the electronic components to the circuit board.
To improve the durability of electrical devices, the gap between the die, package carrier, and/or circuit board is commonly filled with an encapsulant material. Underfilling with encapsulant material may increase the ability of the electrical device to withstand mechanical shock and vibration, protect electrical connections from environmental conditions, and provide improved thermal coupling between the mounted device and the underlying substrate. One method of underfilling involves dispensing a low-viscosity encapsulant material with strong wetting characteristics along a side edge of the gap so that the encapsulant is drawn into the gap by surface tension wetting or capillary action. To improve flow, the viscosity of the encapsulant material may be reduced and the flow rate increased by pre-heating the substrate before the encapsulant material is dispensed onto the substrate. The substrate may be also be heated to cure the encapsulant after the encapsulant has flowed into the gap.
Consequently, there is a need for improved apparatuses and methods for heating substrates in the electronics industry.